access over http proxy

```
making request using http_proxy or https_proxy envorinment variable.
```

Original issue reported on code.google.com by `tadatada...@gmail.com` on 5 Apr 2012 at 6:44

Attachments:
- [gdata.proxy.diff](https://storage.googleapis.com/google-code-attachments/gdata-ruby-util/issue-20/comment-0/gdata.proxy.diff)
